This invention relates generally to inspection methods for identifying structural particularities and, more particularly, to an inspection method for identifying defects, including cracks and corrosion, in aircraft.
xe2x80x9cAging aircraftxe2x80x9d is a Federal Aviation Administration (FAA) classification for a commercial aircraft with over 36,000 cycles on its airframe, or 15 years of service life, or a combination of cycles and years of service life. A cycle comprises a takeoff and landing. Worldwide, there are thousands of aircraft in the xe2x80x9caging aircraftxe2x80x9d category.
The FAA requires that an aging aircraft be inspected for cracks and corrosion at regular intervals. Current known inspection techniques use visual inspection. To prepare for a visual inspection, the interior of the fuselage must be stripped of seats, bins, galleys, panels, and insulation. Further, the visual inspection process itself typically takes several personnel ten days or more to complete. Moreover, it has been found that a crack may not be identified with a visual inspection until it reaches a length of two to four inches. Additionally, cracks and corrosion on the interior layers or frame members cannot be seen at all using visual inspection. Overall, the visual inspection technique is slow, laborious, damaging to aircraft materials, and less than optimally effective for crack and corrosion detection.
Alternative non-invasive inspection techniques, such as x-ray inspection, would provide superior detection of cracks and corrosion in an aircraft fuselage. Additionally, the aircraft""s panels and insulation would not have to be removed. However, there is currently no practical way of performing a comprehensive x-ray inspection of an aircraft. To obtain an x-ray image through a fuselage (or wing) requires that an x-ray source or emitter and an x-ray detector, located inside and outside of the fuselage respectively, be positioned with respect to each other at the time that the images are obtained.
Accordingly, those skilled in the art have long recognized the need for a new method of efficiently performing an inspection of an aircraft. The present invention clearly fulfills these and other needs by providing the means to perform an efficient and non-invasive inspection, reducing the time and cost required to prepare an aircraft for inspection, reducing the time to perform the inspection, and increasing the effectiveness and quality of the inspection. The structure and method of the present invention may also be used to identify components, or particularities, of any structure, including, for example, ships and buildings.
Briefly, and in general terms, the present invention resolves the above and other problems by providing an inspection method for inspecting a structure and identifying particularities, such as defects, in the structure. The inspection method includes: positioning two inspection devices at a pre-determined distance from each other, one of the inspection devices inside of the structure and the other inspection device outside of the structure, wherein the two inspection devices comprise a detector inspection device and a source inspection device; collecting data, such as images, of a portion of the structure located between the source and the detector; moving the inspection devices on the inside and the outside of subsequent portions of the structure to be inspected while maintaining an approximate distance between the inspection devices without reliance on a physical or optical link between the inspection devices; and collecting data of the additional portions of the structure located between the inspection devices.
In accordance with an aspect of the present invention, the inspection devices are automatically moved to each portion of the structure to be inspected according to an inspection sequence that controls the movement of the inspection devices along the structure. In an embodiment, the inspection sequence is a programmed inspection sequence. The programmed inspection sequence that controls movement of the inspection devices along the structure may be produced at some time prior to the inspection by an operator moving one or both of the inspection devices through data collection positions and programming the data collection positions into the inspection sequence. In an embodiment, during the creation of the programmed inspection sequence, sections of the inspection sequence that correspond to similar or substantially similar portions of the structure are repeated within the inspection sequence during the programming, thereby, among other things, simplifying the programming of the inspection sequence.
In an embodiment, the programmed inspection sequence that controls movement of the inspection devices along the structure is produced from surface data generated from visual surveying equipment. In another embodiment, the programmed inspection sequence is produced from surface model data derived from Computer Assisted Design (CAD) data. In yet another embodiment, the source inspection device and the detector inspection device are manually moved to each portion of the structure to be inspected.
In accordance with another aspect of the present invention, the source inspection device comprises an x-ray source and the detector inspection device comprises an x-ray detector. In an embodiment, the source is mounted on a first gantry and the detector is mounted on a second gantry. A gantry is a motion control device that allows positioning of an inspection device at a desired position. A gantry consists of two or more linked mechanical structures, the relative positions of which are controlled by actuators. A construction crane or a xe2x80x9ccherry pickerxe2x80x9d are examples of gantries. The first and second gantries are synchronized to move in coordinated motion with each other under the direction of a gantry control system. Alternatively, it is not required that both gantries move in strict synchronization; it is only required that the inspection devices stop at prescribed relative positions so that satisfactory data, such as images, can be acquired. Either of these types of relative motions will be referred to herein as synchronized motion.
In another embodiment, one inspection device is mounted on an interior gantry that utilizes a track assembly and the other inspection device is mounted on an exterior gantry that utilizes a rover vehicle. A rover vehicle is a ground-based vehicle that carries the external gantry from point to point. In an embodiment, the rover has four-wheel independent steering to increase maneuverability.
In accordance with another aspect of the present invention, the inspection devices are initialized at home positions that allow for direct or visual contact between the inspection devices. In an embodiment, the task of initializing a gantry or inspection device consists of moving the inspection device to a known location and entering into the motion control system the coordinates of the known location either in the gantry or the coordinate system of the structure to be inspected, e.g., the aircraft coordinate system. In another embodiment, the task of initializing a gantry or inspection device consists of moving the gantry to a known internal configuration, or home position, and entering into the motion control system the gantry coordinate system values for that position. In yet another embodiment, the task of initializing a gantry or inspection device consists of moving two inspection devices to specific locations relative to each other and entering into the motion control system the relative coordinates of one or both inspection devices or gantries.
In an embodiment, the structure that the inspection method is designed to inspect comprises an aircraft. Additionally, in an embodiment the particularities that the inspection method identifies comprise cracks and corrosion. In an alternative embodiment, the structure that the inspection method is used to inspect comprises any structure, including, but not limited to, a building or a ship.
Another embodiment of the present invention is also directed towards an inspection method for identifying particularities, such as defects, in a structure. The inspection method includes: placing a first gantry having an attached inspection device in a known position located outside of the structure; placing a second gantry having an attached inspection device inside of the structure, wherein the inspection devices comprise a detector inspection device and a source inspection device; initializing the relative positions of the inspection devices; moving the inspection devices in a coordinated manner to each data, e.g., image, collection position according to an inspection sequence that controls movement of the inspection devices along the structure while maintaining the relative alignment of the inspection devices; and collecting data, e.g., images, of the structure at each data collection position.
In accordance with an aspect of the present invention, the motion of a gantry can be mathematically derived from the desired motion of the respective inspection device, where the desired motion of the inspection device is characterized with respect to an inspection device based coordinate system. The coordinate axis system of the inspection device is defined as a set of artificial axes. The term artificial is used to denote the fact that the inspection device""s coordinate axes typically have no one corresponding gantry motion directly associated with them. Generally, to move an inspection device along one of its artificial axes typically requires that two or more gantry axes be actuated.
In an embodiment, the artificial axes are correlated, or otherwise registered, to the geometry of the structure to be inspected, e.g., the aircraft geometry. The artificial axes allow an operator to move the inspection device in its coordinate system, thereby simplifying the operator""s task of maintaining the inspection device in a constant orientation relative to the surface of the structure to be inspected, e.g., parallel or perpendicular to the aircraft fuselage, at all times as the inspection device is moved along the structure. Without the use of the artificial axes of the inspection device, the operator would be required to characterize the desired motion of the inspection device with respect to the gantry axes, and manually manipulate several gantry axes at the same time while simultaneously attempting to follow the changing geometry of the structure to be inspected, e.g., the aircraft.
In an embodiment, once the position of one of the inspection devices is determined, a corresponding position for the second inspection device is obtained. The position of the second inspection device can be an offset from the first inspection device position. In an embodiment, the offset is the distance between the inspection devices along an artificial axis, such as the normal axis to the first inspection device""s front surface. The required motion of the gantry supporting the second inspection device to move the second inspection device to a designated position can be mathematically derived by a process of reverse kinematics.
Reverse kinematics utilizes the gantry geometry, the location and orientation of the inspection device on the gantry, and the desired position of the inspection device to adjust the gantry actuators appropriately. In an embodiment, reverse kinematics can be utilized to generate a set of motions for a second gantry that will achieve a sequence of data collection positions for the second inspection device corresponding to a programmed sequence of data collection positions for the first inspection device. In an embodiment, reverse kinematics may be utilized to derive a set of interior gantry motions that will achieve a sequence of image collection positions for an x-ray source inspection device corresponding to a programmed sequence of image collection positions for an x-ray detector inspection device, while maintaining the relative alignment and synchronized motion of the inspection devices. In an alternative embodiment, reverse kinematics can be utilized to derive a single position at a time for the second, e.g., source or interior, inspection device, and then repeated to retain synchronization of the second inspection device with the first, e.g., detector or exterior, inspection device for each new position of the first inspection device.
In an embodiment, the data collection, such as imaging, of each portion of the structure under inspection is performed when the motions of the gantries are intermittently stopped.
Another embodiment of the present invention is a method for creating an inspection sequence to be used in inspecting a structure for particularities, such as defects. This method includes: aligning an exterior gantry having an inspection device with the structure to be inspected; initializing all axes of the exterior gantry; creating at least three reference points at known locations on the structure; determining the location and orientation of the inspection device relative to the structure via triangulation to the reference points; determining data, e.g., image, collection positions for the inspection device of the exterior gantry; positioning and orienting the attached inspection device with respect to the structure at the data collection positions and recording the data collection positions; and, using reverse kinematics to derive a set of interior gantry motions that will achieve a sequence of data collection positions for the inspection device on the interior gantry corresponding to a programmed sequence of image collection positions for the inspection device on the exterior gantry, while maintaining the relative alignment and synchronized motion of the inspection devices.
In accordance with an aspect of the present invention, the inspection sequence is programmed to automatically move the inspection devices to each data, e.g., image, collection position on the structure. In an embodiment, the inspection device of the exterior gantry comprises an x-ray detector and the inspection device of the interior gantry comprises an x-ray source. In an embodiment, the exterior gantry is a master system and the interior gantry is a slave system.
Another embodiment of the present invention is an inspection method for identifying particularities, such as defects, in a structure. The inspection method includes: locating an exterior rover gantry having a detector inspection device to a pre-determined home position outside the structure and correlating, or registering, the gantry to the structure; mounting an interior rail gantry having an x-ray source inspection device onto alignment tracks at a pre-determined home position located inside the structure; aligning the detector inspection device of the exterior gantry with the x-ray source inspection device of the interior gantry through physical or optical or other applicable means; implementing an inspection sequence to move the detector inspection device and the source inspection device to each image collection position; and obtaining an x-ray image at each image collection position with the inspection devices. In an embodiment, the inspection sequence is a programmed inspection sequence for automatically moving the detector and source inspection devices to each image collection position. In an embodiment, the inspection method can utilize an alignment system for referencing the structure, including, but not limited to a target alignment system, a laser alignment system, a radio frequency alignment system, a physical alignment systems, or an optical alignment system. Other known alignment techniques may also be utilized.
Another embodiment of the present invention is an inspection system for identifying particularities, such as defects, in a structure. The inspection system includes a coordinated dual gantry system, a source inspection device, a detector inspection device and a gantry control system. The coordinated dual gantry system includes an exterior gantry that is configured to move externally to the structure and an interior gantry that is configured to move internally to the structure in synchronized motion with the exterior gantry. One of the inspection devices is mounted on the exterior gantry and the other inspection device is mounted on the interior gantry. The gantry control system maneuvers the detector inspection device and the source inspection device in synchronized motion with each other to each data, e.g., image, collection position on the structure, according to a programmed inspection sequence that controls movement of the inspection devices along the structure. In an embodiment, the gantry control system maneuvers the detector and source inspection devices while maintaining the relative alignment of the detector and the source at each data collection position. Together the inspection devices collect data, such as an image, from each data collection position on the structure.
In accordance with an aspect of the present invention, the inspection system includes an image acquisition system that controls image collection. In another embodiment, the inspection system includes a sensor or sensors which can accurately determine the location of the detector inspection device with respect to the structure just before data collection takes place. In an embodiment, the inspection system utilizes an alignment system such as, but not limited to, a target alignment system, a laser alignment system, a radio frequency alignment system, a physical alignment system, or an optical alignment system. In an embodiment, the exterior gantry is a master system and the interior gantry is a slave system.
In an embodiment, artificial axes are utilized that allow an operator to move an inspection device in a coordinate system that continually updates in space with respect to the orientation of the inspection device, rather than requiring desired motion of the inspection device to be input with respect to gantry axes. In an embodiment, the artificial axes register to, or are otherwise correlated with, the coordinate system of the structure to be inspected, e.g., the aircraft coordinate system. In an embodiment, reverse kinematics are utilized to derive a set of interior gantry motions that will achieve a sequence of data collection positions for the source inspection device corresponding to a programmed sequence of data collection positions for the detector inspection device, while maintaining the relative alignment and synchronized motion of the inspection devices.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate by way of example, the features of the present invention.